The present invention relates to an azomethine compound. In detail, the invention relates to an azomethine compound suitable for a jet printing ink of magenta color.
In an ink-jet recording method, images or characters are printed on image-receiving material with ink ejected from very fine nozzles. The ink-jet recording method can be conducted by using a relatively inexpensive apparatus (i.e., an ink-jet printer), as compared with other printing methods. Further, in proportion to improvement of the method, images of high qualities have been given recently. Now, the ink-jet recording method is one of the most popular image-recording methods.
Ink for the ink-jet recording method (i.e., jet printing ink) must not choke the fine nozzles. Since aqueous inks (aqueous solutions of dyes) hardly choke the nozzles, they are widely used. However, the aqueous inks have poor water resistance. Various means (described in Japanese Patent Provisional Publication Nos. 4(1992)-28776, 4(1992)-189876, 4(1992)-261478, 4(1992)-359071 and 4(1992)-359072) have been proposed to improve the water resistance of the aqueous inks or water-soluble dyes. in addition, the water-soluble dyes have poor light resistance.
Oil-soluble dyes (described in Japanese Patent Provisional Publication Nos. 1(1989)-170672, 3(1991)-221137, 7(1995)-96163, 8(1996)-218015, 9(1997)-3376, 9(1997)-241565, 9(1997)-286939 and 10(1998)-279873) have been proposed in place of the water-soluble dyes. The oil-soluble dyes are usually incorporated in microcapsules or soaked in polymers when they are used for ink-jet printing. Although the oil-soluble dyes have satisfying water resistance, they are unsatisfactory in color reproduction and color stability.
Water-soluble dyes for ink-jet recording have poor resistance against water and light, while oil-soluble dyes are unsatisfactory in color reproduction and color stability.
An object of the present invention is to provide an oil-soluble dye excellent in color reproduction and color stability.
Another object of the invention is to provide an azomethine compound suitable for a jet printing ink of magenta color.
A further object of the invention is to provide an oily magenta ink for ink-jet recording.
The applicants.have found an azomethine compound having light-absorption characteristics suitable for a magenta dye. The compound is oil-soluble, and is advantageously used in a preparation of an oily magenta ink for ink-jet recording.
The present invention provides an azomethine compound represented by the formula (I): 
wherein 
R1 is an alkyl group having 1 to 16 carbon atoms; R2 is a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an amido group having 2 to 20 carbon atoms, an alkoxycarbonylamino group having 2 to 20 carbon atoms, nitro or cyano; R3 is an alkyl group having 1 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, an aryloxyalkyl group having 7 to 30 carbon atoms or an alkoxycarbonylalkyl group having 3 to 30 carbon atoms; R4 is an alkyl group having 1 to 16 carbon atoms; L1 is an alkylene group having 1 to 30 carbon atoms or an arylene group having 6 to 30 carbon atoms; L2 is xe2x80x94COxe2x80x94NHxe2x80x94, xe2x80x94SO2xe2x80x94NHxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94 or xe2x80x94Oxe2x80x94COxe2x80x94NHxe2x80x94; X is cyano, an alkoxycarbonyl group having 2 to 19 carbon atoms, an alkylsulfonyl group having 1 to 18 carbon atoms, an arylsulfonyl group having 6 to 26 carbon atoms, sulfamoyl, an alkylsulfamoyl group having 1 to 18 carbon atoms or an arylsulfamoyl group having 6 to 26 carbon atoms; Y is hydrogen, a halogen atom, hydroxyl, an alkoxy group having 1 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms or an acyloxy group having 2 to 20 carbon atoms; m is 1, 2, 3 or 4; n is an integer of 1 to 18; p is 0, 1, 2, 3 or 4; and R1, L1, L2, R3 and R4 have 20 to 50 carbon atoms in total.
The invention also provides an oily magenta ink in which an azomethine dye represented by the formula (I) is dissolved in an organic solvent.
The azomethine compound represented by the formula (I)has excellent characteristics suitable for a magenta dye. Accordingly, the azomethine compound can be advantageously used in a preparation of an oily magenta ink for ink-jet recording.
Further, the azomethine compound represented by the formula (I) is excellent in stability to light and heat. Accordingly, the azomethine compound can be used a magenta dye that is excellent in a light resistance and in a heat resistance.
The azomethine compound represented by the formula (I) can be classified into the three embodiments represented by the formulas (Ia), (Ib) and (Ic), respectively. The embodiment of the formula (Ia) is particularly preferred. 
In the formulas (Ia) to (Ic), R1 is an alkyl group having 1 to 16 carbon atoms. The alkyl group preferably has 1 to 12 carbon atoms, more preferably has 1 to 8 carbon atoms, further preferably has 1 to 6 carbon atoms, and most preferably has 1 to 4 carbon atoms. The alkyl group can have a branched chain. Examples of the alkyl groups include methyl and t-butyl.
In the formulas (Ia) to (Ic), R2 is a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an amido group having 2 to 20 carbon atoms, an alkoxycarbonylamino group having 2 to 20 carbon atoms, nitro or cyano.
The alkyl group preferably has 1 to 12 carbon atoms, more preferably has 1 to 8 carbon atoms, further preferably has 1 to 4 carbon atoms, and most preferably has 1 or 2 carbon atoms. The alkyl group can have a branched chain. Examples of the alkyl groups include methyl and ethyl.
The alkoxy group preferably has 1 to 12 carbon atoms, more preferably has 1 to 8 carbon atoms, further preferably has 1 to 4 carbon atoms, and most preferably has 1 or 2 carbon atoms. The alkoxy group can have a branched chain. Examples of the alkoxy groups include methoxy.
The amido group preferably has 2 to 12 carbon atoms, more preferably has 2 to 8 carbon atoms, further preferably has 2 to 6 carbon atoms, and most preferably has 3 or 4 carbon atoms. Examples of the amido groups include acetamido.
The alkoxycarbonylamino group preferably has 2 to 12 carbon atoms, more preferably has 2 to 8 carbon atoms, further preferably has 2 to 6 carbon atoms, and most preferably has 2 or 3 carbon atoms. Examples of the alkoxycarbonylamino groups include methoxycarbonylamino.
In the formulas (Ia) to (Ic), R3 is an alkyl group having 1 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, an aryloxyalkyl group having 7 to 30 carbon atoms or an alkoxylcarbonylalkyl group having 3 to 30 carbon atoms.
The alkyl group preferably has 2 to 25, more preferably has 3 to 20 carbon atoms, and most preferably has 4 to 16 carbon atoms. The alkyl group can have a branched chain.
Examples of the aryl groups include phenyl and naphthyl. Phenyl is preferred. The aryl group can have a substituent group. Examples of the substituent groups include a halogen atom, an alkyl group having 1 to 24 carbon atoms and an alkoxy group having 1 to 24 carbon atoms. The aryl group has 6 to 30 carbon atoms, preferably 6 to 25 carbon atoms, more preferably 6 to 20 carbon atoms, and most preferably 6 to 16 carbon atoms. The number of the carbon atoms means the number of the total carbon atoms contained in the aryl group and the substituent group.
The alkyl moiety of the aryloxyalkyl group can have a branched chain. The aryl moiety of the aryloxyalkyl group is preferably phenyl. The aryloxyalkyl group can have a substituent group. Examples of the substituent groups include a halogen atom, an alkyl group having 1 to 23 carbon atoms and an alkoxy group having 1 to 23 carbon atoms. The aryloxyalkyl group has 7 to 30 carbon atoms, preferably has 7 to 25 carbon atoms, more preferably 7 to 20 carbon atoms, and further preferably 7 to 16 carbon atoms. The number of the carbon atoms means the number of the total carbon atoms contained in the aryloxyalkyl group and the substituent group.
The alkoxycarbonylalkyl group preferably has 3 to 25 carbon atoms, more preferably has 4 to 20 carbon atoms, and most preferably has 5 to 16 carbon atoms. Each of the two alkyl moieties of the alkoxycarbonylalkyl group can have a branched chain.
In the formula (Ic), R4 is an alkyl group having 1 to 16 carbon atoms. The alkyl group preferably has 1 to 12 carbon atoms, more preferably has 1 to 8 carbon atoms, further preferably has 1 to 6 carbon atoms, and most preferably has 1 to 4 carbon atoms. The alkyl group can have a branched chain. Examples of the alkyl groups include methyl and ethyl.
In the formulas (Ia) to (Ic), L1 is an alkylene group having 1 to 30 carbon atoms or an arylene group having 6 to 30 carbon atoms.
The alkylene group preferably has 1 to 25 carbon atoms, more preferably has 2 to 20 carbon atoms, and most preferably has 2 to 16 carbon atoms. The alkylene group can have a branched chain.
Examples of the arylene groups include phenylene and naphthylene. Phenylene is preferred. The arylene group can have a substituent group. Examples of the substituent groups include a halogen atom, an alkyl group having 1 to 24 carbon atoms and an alkoxy group having 1 to 24 carbon atoms. The arylene group has 6 to 30 carbon atoms, preferably 6 to 25 carbon atoms, more preferably 6 to 20 carbon atoms, and most preferably 6 to 16 carbon atoms. The number of the carbon atoms means the number of the total carbon atoms contained in the arylene group and the substituent group. In the formulas (Ia) to (Ic), L2 is xe2x80x94COxe2x80x94NHxe2x80x94, xe2x80x94SO2xe2x80x94NHxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94 or xe2x80x94Oxe2x80x94COxe2x80x94NHxe2x80x94, in each of which the left side is attached to R3, and the right side is attached L1.
In the formulas (Ia) to (Ic), X is cyano, an alkoxycarbonyl group having 2 to 19 carbon atoms, an alkylsulfonyl group having 1 to 18 carbon atoms, an arylsulfonyl group having 6 to 26 carbon atoms, sulfamoyl, an alkylsulfamoyl group having 1 to 18 carbon atoms or an arylsulfamoyl group having 6 to 26 carbon atoms. Cyano and an alkoxycarbonyl group having 2 to 19 carbon atoms are preferred, and cyano is most preferred.
The alkoxycarbonyl group preferably has 2 to 8 carbon atoms. Examples of the alkoxycarbonyl groups include methoxycarbonyl and dodecyloxycarbonyl.
The alkylsulfonyl group preferably has 1 to 7 carbon atoms. Examples of the alkylsulfonyl groups include methanesulfonyl.
The aryl moiety of the arylsulfonyl group is preferably phenyl. The arylsulfonyl group can have a substituent group. Examples of the substituent groups include a halogen atom, an alkyl group having 1 to 20 carbon atoms and an alkoxy group having 1 to 20 carbon atoms. The arylsulfonyl group has 6 to 26 carbon atom, and preferably has 6 to 15 carbon atoms. The number of the carbon atoms means the number of the total carbon atoms contained in the arylsulfonyl group and the substituent group. Examples of the arylsulfonyl groups include benzenesulfonyl.
The alkylsulfamoyl group preferably has 1 to 9 carbon atoms. Examples of the alkylsulfamoyl groups include methylsulfamoyl.
The aryl moiety of the arylsulfamoyl group is preferably phenyl. The arylsulfamoyl group can have a substituent group. Examples of the substituent groups include a halogen atom, an alkyl group having 1 to 20 carbon atoms and an alkoxy group having 1 to 20 carbon atoms. The arylsulfamoyl group has 6 to 26 carbon atoms, and preferably has 6 to 15 carbon atoms. The number of the carbon atoms means the number of the total carbon atoms contained in the arylsulfamoyl group and the substituent group. Examples of the arylsulfamoyl groups include phenylsulfamoyl.
In the formulas (Ia) to (Ic), Y is hydrogen, a halogen atom, hydroxyl, an alkoxy group having 1 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms or an acyloxy group having 2 to 20 carbon atoms. Hydrogen atom is particularly preferred.
The alkoxy group preferably has 1 to 12 carbon atoms, more preferably has 1 to 8 carbon atoms, further preferably has 1 to 4 carbon atoms, and most preferably has 1 or 2 carbon atoms. The alkoxy group can have a branched chain. Examples of the alkoxy groups include methoxy and ethoxy.
The aryl moiety of the aryloxy group is preferably phenyl. The aryloxy group can have a substituent group. Examples of the substituent groups include a halogen atom, an alkyl group having 1 to 14 carbon atoms and an alkoxy group having 1 to 14 carbon atoms. The aryloxy group has 6 to 20 carbon atoms, and preferably has 6 to 15 carbon atoms. The number of the carbon atoms means the number of the total carbon atoms contained in the aryloxy group and the substituent group. Examples of the aryloxy groups include phenoxy.
The acyloxy group preferably has 1 to 12 carbon atoms, more preferably has 1 to 8 carbon atoms, further preferably has 1 to 4 carbon atoms, and most preferably has 2 or 3 carbon atoms. Examples of the acyloxy groups include acetoxy.
In the formulas (Ia) to (Ic), m is an integer of 1 to 4, preferably is an integer of 1 to 3, and more preferably is 1 or 2. In the case that m is 2, 3 or 4, (CH2)m means an alkylene group of a straight chain.
In the formulas (Ia) to (Ic), n is an integer of 1 to 18, preferably is an integer of 1 to 14, more preferably is an integer of 1 or 10, further preferably is an integer of 1 to 8, and most preferably is an integer of 1 to 6. In the case that n is 2 or more, the alkylene group represented by CnH2n can have a branched chain.
In the formulas (Ia) to (Ic), p is 0, 1, 2, 3 or 4, preferably is 0, 1, 2 or 3, more preferably is 0, 1 or 2, further preferably is 0 or 1, and most preferably is 0. In the case that p is 2, 3 or 4, the groups represented by R2 can be different from each other.
In the formulas (Ia) and (Ib), R1, L1, L2 and R3 have 20 to 50 carbon atoms in total. In the formula (Ic), R1, L1, L2, R3 and R4 have 20 to 50 carbon atoms in total. The total number of the carbon atoms preferably is 25 to 45.
The azomethine compound of the formula (I) preferably has a molecular weight of 600 to 2,000, and more preferably has a molecular weight of 800 to 1,500.
Examples of the azomethine compounds represented by the formula (I) are shown below. 
(Ia-1)
R1: CH3, R21: H, R22: H,
R3: 1-(2,4-di-t-pentylphenoxy)heptyl,
L1: xe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94, L2: xe2x80x94COxe2x80x94NHxe2x80x94, X: cyano,
Y: H, m: 2, n: 2,
Total number of carbon atoms in R1, L1, L2 and R3: 28
(Ia-2)
R1: CH3, R21: H, R22: H,
R3: 2-octyloxy-5-t-octylphenyl,
L1: xe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94, L2: xe2x80x94SO2xe2x80x94NHxe2x80x94, X: cyano,
Y: H, m: 2, n: 4,
Total number of carbon atoms in R1, L1, L2 and R3: 26
(Ia-3)
R1: CH3, R21: H, R22: H,
R3: 2-octyloxy-5-(2-octyloxy-5-t-octylphenylsulfoneamido)phenyl,
L1: xe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94, L2: xe2x80x94SO2xe2x80x94NHxe2x80x94, X: cyano,
Y: H, m: 2, n: 1,
Total number of carbon atoms in R1, L1, L2 and R3: 40
(Ia-4)
R1: CH3, R21: H, R22: H,
R3: 2-tetradecyloxycarbonylethyl,
L1: xe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94, L2: xe2x80x94COxe2x80x94NHxe2x80x94,
X: ethoxycarbonyl, Y: H, m: 2, n: 4,
Total number of carbon atoms in R1, L1, L2 and R3: 22
(Ia-5)
R1: CH3, R21: CH3, R22: H, R3: pentadecyl,
L1: -1,4-phenylene-, L2: xe2x80x94COxe2x80x94NHxe2x80x94, X: cyano,
Y: H, m: 2, n: 4,
Total number of carbon atoms in R1, L1, L2 and R3: 23
(Ia-6)
R1: CH3, R21: CH3, R22: H,
R3: 1-(2,4-di-t-pentylphenoxy)heptyl,
L1: xe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94, L2: xe2x80x94COxe2x80x94NHxe2x80x94, X: cyano,
Y: OH, m: 2, n: 2,
Total number of carbon atoms in R1, L1, L2 and R3: 28
(Ia-7)
R1: CH3, R21: H, R22: H, R3: octadecyl,
L1: xe2x80x94CH2xe2x80x94CH2xe2x80x94, L2: xe2x80x94Oxe2x80x94, X: methoxycarbonyl,
Y: H, m: 1, n: 2,
Total number of carbon atoms in R1, L1, L2 and R3: 21
(Ia-8)
R1: CH3, R21: H, R22: H, R3: hexadecyl,
L1: -1,3-phenylene-, L2: xe2x80x94Oxe2x80x94COxe2x80x94, X: cyano,
Y: H, m: 3, n: 4,
Total number of carbon atoms in R1, L1, L2 and R3: 24
(Ia-9)
R1: t-C4H9, R21: H, R22: H,
R3: 1-(2,4-di-t-pentylphenoxy)pentyl,
L1: xe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94, L2: xe2x80x94COxe2x80x94NHxe2x80x94, X: cyano,
Y: H, m: 2, n: 2,
Total number of carbon atoms in R1, L1, L2 and R3: 29
(Ia-10)
R1: t-C4H9, R21: H, R22: H,
R3: 2-(2-methoxy)ethoxy-5-t-octylphenyl,
L1: xe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94, L2: xe2x80x94SO2xe2x80x94NHxe2x80x94, X: cyano,
Y: H, m: 2, n: 4,
Total number of carbon atoms in R1, L1, L2 and R3: 24
(Ia-11)
R1: t-C4H9, R21: H, R22: H, R3: tridecyl,
L1: -1,3-phenylene-, L2: xe2x80x94COxe2x80x94NHxe2x80x94, X: cyano,
Y: H, m: 2, n: 2,
Total number of carbon atoms in R1, L1, L2 and R3: 24
(Ia-12)
R1: t-C4H9, R21: H, R22: H,
R3: 2-tetradecyloxycarbonylethyl,
L1: -1,4-phenylene-, L2: xe2x80x94COxe2x80x94NHxe2x80x94, X: cyano,
Y: H, m: 2, n: 4,
Total number of carbon atoms in R1, L1, L2 and R3: 28
(Ia-13)
R1: t-C4H9, R21: H, R22: H,
R3: 1-(2,4-di-t-pentylphenoxy)heptyl,
L1: -1,4-phenylene-, L2: xe2x80x94COxe2x80x94NHxe2x80x94, X: cyano,
Y: H, m: 2, n: 2,
Total number of carbon atoms in R1, L1, L2 and. R3: 34
(Ia-14)
R1: t-C4H9, R21: H, R22: H,
R3: 1-(2,4-di-t-pentylphenoxy)heptyl,
L1: -1,4-phenylene-, L2: xe2x80x94COxe2x80x94NHxe2x80x94, X: cyano,
Y: H, m: 2, n: 4,
Total number of carbon atoms in R1, L1, L2 and R3: 34
(Ia-15)
R1: t-C4H9, R21: CH3, R22: H,
R3: 1-(2,4-di-t-pentylphenoxy)heptyl,
L1: -1,4-phenylene-, L2: xe2x80x94COxe2x80x94NHxe2x80x94, X: cyano,
Y: OH, m: 2, n: 2,
Total number of carbon atoms in R1, L1, L2 and R3: 34
(Ia-16)
R1: t-C4H9, R21: CH3, R22: H,
R3: 2-tetradecyloxycarbonylethyl,
L1: -1,4-phenylene-, L2: xe2x80x94COxe2x80x94NHxe2x80x94, X: cyano,
Y: H, m: 2, n: 4,
Total number of carbon atoms in R1, L1, L2 and R3: 28
(Ia-17)
R1: t-C4H9, R21: CH3, R22: H, R3: heptadecyl,
L1: -1,2-phenylene-, L2: xe2x80x94COxe2x80x94NHxe2x80x94,
X: methoxycarbonyl, Y: H, m: 1, n: 1,
Total number of carbon atoms in R1, L1, L2 and R3: 28
(Ia-18)
R1: t-C4H9, R21: NHCOCH3, R22: H,
R3: hexadecyl, L1: -1,3-phenylene-,
L2: xe2x80x94SO2xe2x80x94NHxe2x80x94, X: cyano, Y: acetoxy,
m: 1, n: 2,
Total number of carbon atoms in R1, L1, L2 and R3: 26
(Ia-19)
R1: t-C4H9, R21: OCH3, R22: H,
R3: octadecyl, L1: -1,4-phenylene-,
L2: xe2x80x94Oxe2x80x94, X: sulfamoyl, Y: phenoxy,
m: 3, n: 2,
Total number of carbon atoms in R1, L1, L2 and R3: 28
(Ia-20)
R1: t-C4H9, R21: H, R22: OCH3,
R3: hexadecyl, L1: -3-chloro-1,4-phenylene-,
L2: xe2x80x94Oxe2x80x94, X: methanesulfonyl, Y: methoxy,
m: 4, n: 2,
Total number of carbon atoms in R1, L1, L2 and R3: 26
(Ia-21)
R1: C2H5, R21: H, R22: H, R3: pentadecyl,
L1: xe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94, L2: xe2x80x94COxe2x80x94NHxe2x80x94, X: cyano,
Y: H, m: 2, n: 2,
Total number of carbon atoms in R1, L1, L2 and R3: 21
(Ia-22)
R1: C3H7, R21: H, R22: H, R3: pentadecyl,
L1: xe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94, L2: xe2x80x94COxe2x80x94NHxe2x80x94, X: cyano,
Y: H, m: 2, n: 4,
Total number of carbon atoms in R1, L1, L2 and R3: 22
(Ia-23)
R1: C7H15, R21: CH3, R22: H,
R3: 2-tetradecyloxycarbonylethyl,
L1: -1,4-phenylene-, L2: xe2x80x94COxe2x80x94NHxe2x80x94, X: cyano,
Y: H, m: 2, n: 4,
Total number of carbon atoms in R1, L1, L2 and R3: 31
(Ia-24)
R1: C4H9, R21: H, R22: H,
R3: 2-tetradecyloxycarbonylethyl,
L1: -1,4-phenylene-, L2: xe2x80x94COxe2x80x94NHxe2x80x94,
X: butoxycarbonyl, Y: H, m: 2, n: 2,
Total number of carbon atoms in R1, L1, L2 and R3: 28
(Ia-25)
R1: C3H7, R21: H, R22: H,
R3: 2-tetradecyloxycarbonylethyl,
L1: -1,4-phenylene-, L2: xe2x80x94COxe2x80x94NHxe2x80x94, X: cyano,
Y: OH, m: 3, n: 2,
Total number of carbon atoms in R1, L1, L2 and R3: 27
(Ia-26)
R1: C2H5, R21: H, R22: H,
R3: 2-tetradecyloxycarbonylethyl,
L1: -1,4-phenylene-, L2: xe2x80x94COxe2x80x94NHxe2x80x94,
X: cyano, Y: methoxy, m: 3, n: 2,
Total number of carbon atoms in R1, L1, L2 and R3: 26 
(Ib-1)
R1: CH3, R2: H,
R3: 1-(2,4-di-t-butylphenoxy)heptyl,
L1: -1,3-phenylene-, L2: xe2x80x94COxe2x80x94NHxe2x80x94,
X: methanesulfonyl, Y: H, m: 2, n: 4,
Total number of carbon atoms in R1, L1, L2 and R3: 29
(Ib-2)
R1: CH3, R2: CH3, R3: tetradecyl,
L1: -3-chloro-1,4-phenylene-, L2: xe2x80x94Oxe2x80x94,
X: cyano, Y: OH, m: 2, n: 2,
Total number of carbon atoms in R1, L1, L2 and R3: 21
(Ib-3)
R1, CH3, R2: NHCO2CH3, R3: hexadecyl,
L1: -1,2-phenylene-, L2: xe2x80x94Oxe2x80x94,
X: sulfamoyl, Y: H, m: 2, n: 1,
Total number of carbon atoms in R1, L1, L2 and R3: 23
(Ib-4)
R1: CH3, R2: CN, R3: pentadecyl,
L1: xe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94, L2: xe2x80x94COxe2x80x94NHxe2x80x94,
X: N,N-dimethylsulfamoyl, Y: H,
m: 4, n: 1,
Total number of carbon atoms in R1, L1, L2 and R3: 20 
(Ic-1)
R1: CH3, R3: heptadecyl, R4: CH3,
L1: xe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94, L2: xe2x80x94COxe2x80x94NHxe2x80x94, X: cyano,
Y: H, m: 2, n: 4,
Total number of carbon atoms in R1, L1, L2, R3 and R4: 23
(Ic-2)
R1: t-C4H9, R3: 2-tetradecyloxycarbonylethyl,
R4: C2H5, L1: -1,4-phenylene-,
L2: xe2x80x94Oxe2x80x94COxe2x80x94NHxe2x80x94, X: cyano, Y: H,
m: 2, n: 4,
Total number of carbon atoms in R1, L1, L2, R3 and R4: 30
The azomethine compound of the formula (I) can be synthesized by referring to the method described in Japanese Patent Provisional Publication No. 4(1992)-126772. The azomethine compound can be synthesized by a reaction of an azole compound represented by the formula (II) with a p-phenylenediamine compound represented by the formula (III) under an oxidizing condition. 
In the formulas (II) and (III), Z1, Z2, R1, R2, X, Y, m, n and p are the same as those described above for the formula (I); and R is a group eliminable in the reaction. Examples of the eliminable groups (R) include hydrogen, a halogen atom, a heterocyclic group and an aryloxy group.
Though a dye of the azomethine compound of the formula (I) has excellent light resistance, an anti-fading agent can further improve its light resistance. The anti-fading agent is described in xe2x80x9cShikizai (written in Japanese)xe2x80x9d, 797, 70(1997). Particularly preferred examples of the anti-fading agents are spirochroman and spiroindane.
The azomethine compound of the formula (I) is preferably used as a magenta dye, particularly an oily magenta ink suitably used for ink-jet recording.
The oily magenta ink for ink-jet recording can be easily prepared according to known publications (for example, Japanese Patent Provisional Publication Nos. 3(1991)-231975, 11(1999)-158422, 11(1999)-172183).
Organic solvents employable for preparing the oily magenta ink are hydrocarbons, alcohols, ketones, ethers, esters, nitrites, amides, sulfoxides and sulfones. Esters and ketones are particularly preferred.
Examples of the hydrocarbons include petroleum ether, petroleum benzine, tetralin, decalin, 1-amylbenzene and methylnaphthalene.
Examples of the alcohols include ethanol, pentanol, heptanol, octanol, cyclohexanol, benzyl alcohol, phenylethyl alcohol, phenylpropyl alcohol, anise alcohol, ethylene glycol monoethyl ether, ethylene glycol monophenyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monoethyl ether, propylene glycol monophenyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether and tripropylene glycol monoethyl ether.
Examples of the ketones include methyl ethyl ketone, benzyl methyl ketone, diacetone alcohol and cyclohexanone.
Examples of the ethers include butyl phenyl ether, benzyl ethyl ether and hexyl ether.
Examples of the esters include ethyl acetate, amyl acetate, benzyl acetate, phenylethyl acetate, phenoxyethyl acetate, ethyl phenylacetate, benzyl propionate, ethyl benzoate, butyl benzoate, ethyl laurate, butyl laurate, isopropyl myristate, isopropyl palmitate, triethyl phosphate, tributyl phosphate, diethyl phthalate, diethyl malonate, dipropyl malonate, diethyl diethylmalonate, diethyl succinate, dibutyl succinate, diethyl glutarate, diethyl adipate, dibutyl adipate, di(2-methoxyethyl) adipate, diethyl sebacate, diethyl maleate, dibutyl maleate, dioctyl maleate, diethyl fumarate, dioctyl fumarate, 3-hexenyl cinnamate, ethylene glycol diacetate, ethylene glycol monoethyl ether acetate and propylene glycol diacetate.
Examples of the nitriles include acetonitrile.
Examples of the amides include formamide, N,N-di-methylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-vinyl-2 -pyrrolidone and N,N-diethyldodecaneamide.
Examples of the sulfoxides include dimethyl sulfoxide.
Examples of the sulfones include sulfolane.
Two or more organic solvents can be used in combination.
The oily magenta ink contains the azomethine compound preferably in an amount of 0.2 to 20 wt. %, and more preferably in an amount of 0.5 to 10 wt. %.
In addition to the azomethine compound and the organic solvent, the ink can contain additives such as viscosity controlling agent, surface tension controlling agent, specific resistance controlling agent, film-formation controlling agent, UV absorber, antioxidizing agent, anti-fading agent, anti-fungal agent, rust inhibitor, dispersing agent and surface active agent.
In ink-jet recording, droplets of the aforementioned oily magenta ink (jet printing ink) are ejected to record an image on recording paper (image-receiving material). In this case, the ink preferably has a viscosity of not more than 40 cp and a surface tension of 20 to 100 dyn/cm.
For forming a full-color image, oily inks of cyan and yellow hues can be used together with the oily magenta ink. Further, an oily ink of black hue can be used to control the tone of the image.
As the recording paper (image-receiving material) for ink-jet printing, coat paper is preferred from the view-points of quality and durability of the image. Recording paper containing polymer mordant is also preferred. The recording paper may contain an inorganic pigment. The recording paper preferably comprises a hydrophilic ink-receiving layer containing a hydrophilic binder. The binder is preferably hardened with a curing agent. Further, the recording paper may contain a matting agent. The layers constituting the recording paper may contain a surface active agent or an organic fluorine compound, and further may contain a polymer latex, anti-fading agent and a fluorescent whitening dye.
Ink-jet recording is usually conducted in an on-demand system or in a continuous system. As the head for ink-jet recording (i.e., jet head), some types such as bubble jet type, thermal jet type and ultrasonic type are known.
There are also some types of the ink-jet recording method. For example, in one type, many small droplets of thin ink (which is often referred to as xe2x80x9cphoto-inkxe2x80x9d) are jetted out. In another type, two or more inks having the same hue but different concentrations are used to improve image quality. Further, colorless and transparent ink can be also usable.